Suture rings for rotatable artificial heart valves

ABSTRACT

A suture ring for a rotatable artificial heart valve apparatus has a ring member covered by a fabric material. A portion of the fabric material covers a portion of the inner surface of the ring member. At least one protuberance is formed on the inner surface of the ring member so as to mitigate the frictional resistance to rotation which results from compression of the fabric between the suture ring and the heart valve. Thus, desirable rotation of the heart valve relative to the suture ring is assured over a range of thicknesses of the fabric material.

RELATED APPLICATION

The present application is a continuation of Ser. No. 08/688,672, filedJul. 29, 1996, which has now issued as U.S. Pat. No. 5,755,783.

FIELD OF THE INVENTION

The present invention relates generally to medical devices and moreparticularly to heart valve prostheses having improved suture ringswhich facilitate consistent rotatability of the heart valve body withinthe suture ring.

BACKGROUND OF THE INVENTION

The prior art has included many prosthetic mechanical heart valves whichmay be surgically implanted to replace malfunctioning or diseasedendogenous anatomical heart valves.

Among the prosthetic mechanical heart valves of the prior art areincluded a number of "rotatable" valves. These rotatable valvestypically comprise an annular valve body having one or more occluderleaflets pivotally mounted within the annular valve body such that theleaflet(s) will open and close in response to hemodynamic forces of theblood. In this regard, the leaflets move back and forth between an openposition whereby blood is permitted to outflow through the annular valvebody, and a closed position whereby blood is prevented from backflowingthrough the annular valve body. A needle-penetrable suture ring ismounted about the outer surface of the annular valve body, and issutured directly to the endogenous valve annulus of the patient-host.After the suture ring has been firmly sutured to the host tissue, thesurgeon may manually rotate the valve body to place the occluderleaflets of the valve in their desired orientation prior to completionof the surgical procedure. Thus, it is necessary for the annular valvebody to remain freely rotatable within the suture ring, to facilitatesuch manual rotation of the valve body by the surgeon. If the annularvalve body does not freely rotate within the suture ring, it may benecessary for the surgeon to apply excessive pressure or torque toeffect the desired rotation of the annular valve body. The applicationof excessive pressure or torque to the annular valve body carries a riskof: a) damaging the valve; or b) tearing the sutures which hold thesuture ring of the annular valve body in affixation to the host tissue.

In view of the risks associated with the application of excessivepressure or torque to the annular valve body, it is desirable forrotatable prosthetic heart valves to be designed such that the amount ofpressure or torque required to effect rotation of the annular valve bodywithin the suture ring is consistently within acceptable limits, therebyavoiding any need for the application of excessive pressure or torqueduring the surgical procedure.

One example of a rotatable prosthetic heart valve of the prior art isdescribed in U.S. Pat. No. 4,892,540 (Villana) and is manufactured andsold in at least some countries of the world as the Sorin Bicarbon™Valve, by Sorin Biomedica S.p.A., Saluggia, Italy. The rotatableprosthetic heart valve of U.S. Pat. No. 4,892,540 (Villana) comprises anannular valve body having a pair of leaflets pivotally mountedtherewithin, and an annular suture ring rotatably mounted therearound.An annular suture ring tracking groove is formed in the outer surface ofthe annular valve body. The suture ring is formed of a rigid inner ringmember having an annular tracking rib formed on the inner surfacethereof, and a woven or knitted fabric cover. The annular tracking ribof the rigid suture ring member is snap-fit into the annular trackinggroove formed in the outer surface of the valve body. In this manner,the engagement of the tracking rib within the tracking groove serves tohold the suture ring in substantially fixed longitudinal position on thevalve body, while allowing the suture ring to remain rotatable relativeto the valve body. The fabric cover of the suture ring extends partiallybetween the outer surface of the annular valve body, and the adjacentrigid suture ring member. In this regard, a portion of the fabricmaterial is interposed or captured between the outer surface of theannular valve body and the adjacent inner surface of the rigid ringmember. As a result, variations in the thickness of the fabric materialused in the manufacture of the suture ring may result in variations inthe amount of pressure or torque required to effect rotation of theannular valve body within the suture ring. For example, if the fabricused in the manufacture of the suture ring is relatively thin, verylittle frictional drag will result from the interposition of the fabricbetween the outer surface of the annular valve body and the innersurface of the rigid suture ring member, thereby allowing the annularvalve body to be rotated with minimal force or torque. On the otherhand, if the fabric material used in the manufacture of the suture ringis relatively thick, a greater amount of frictional drag will resultfrom the interposition of the fabric material between the outer surfaceof the annular valve body and the inner surface of rigid suture ringmember, thereby causing excessive force or torque to be required toeffect rotation of the annular valve body within the suture ring.

In view of the above-explained potential for variations in fabricthickness in the suture rings to result in corresponding variations inthe amount of force or torque required to effect rotation of the annularvalve body, it is desirable to design alternative constructions for theannular valve body and/or suture ring to minimize the effect ofvariations in fabric thickness on the amount of pressure or torquerequired to effect rotation of the valve within the suture ring.

SUMMARY OF THE INVENTION

The present invention comprises an improvement in the mode ofconstruction and design of rotatable prosthetic heart valves so as tominimize or prevent untoward variations in the force required to rotatethe valve within the suture ring, irrespective of normal variations inthe thickness of the fabric which covers the suture ring and which is atleast partially interposed between the outer surface of the annularvalve body and the rigid inner frame or ring member of the suture ringmounted thereon. Broadly stated, the improvement of the presentinvention comprises the formation of one or more protuberances on therigid suture ring member and/or the annular valve body to mitigate thesurface area between which the fabric material will be pinched orcaptured.

In accordance with the present invention, there is provided a suturering which is rotatably mountable on a prosthetic heart valve of thetype comprising an annular valve body having one or more occluderleaflets mounted therewithin, and wherein the annular valve body has anouter surface whereupon the rotatable suture ring is mountable. At leastone protuberance (e.g., an annular rib) is formed on either the innersurface of the rigid suture ring member or the outer surface of theannular valve body, adjacent the region(s) wherebetween the fabricmaterial will be pinched or captured. The formation of suchprotuberance(s) on either the outer surface of the annular heart valvebody or the inner surface of the rigid suture ring member serves todecrease the total surface area of these components between which thefabric material will be pinched or captured. In this regard, theprovision of such protuberance(s) will lessen the amount of frictionalresistance to suture ring rotation which will occur as the thickness ofthe fabric material increases.

Further in accordance with the invention, there is provided a rotatableheart valve of the foregoing character, comprising an annular valve bodyhaving at least one occluder leaflet pivotally mounted therewithin, anda rotatable suture ring of the present invention rotatably mounted onthe outer surface thereof. The fabric covering of the suture ring is atleast partially interposed between the outer surface of the annularvalve body and the inner surface of the rigid suture ring member, suchthat the fabric-contacting surface area is no more than 20% of the totalsurface which would otherwise be in direct contact with, and creatingfriction with, the fabric if the friction-mitigating protuberances) werenot present.

Further objects and advantages of the present invention will becomeapparent to those skilled in the art upon reading and understanding thefollowing detailed description of a presently preferred embodiment ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a distal perspective view of a suture ring for a rotatableartificial mitral valve according to the present invention;

FIG. 2 is an exploded distal perspective view of the suture ring of FIG.1, additionally showing the mitral valve in phantom;

FIG. 3 is an enlarged cross sectional view of the ring member of thesuture ring of FIG. 2, taken along line 3 thereof;

FIG. 3a is an enlarged fragmentary perspective view of the annularsponge of FIG. 2, taken within line 3a thereof;

FIG. 4 is a distal perspective view of a suture ring for a rotatableartificial aortic valve according to the present invention;

FIG. 5 is an exploded distal perspective view of the suture ring of FIG.4, additionally showing the aortic valve in phantom;

FIG. 6 is a cross sectional view of the suture ring of FIG. 1;

FIG. 7 is a cross section view of the suture ring of FIG. 4;

FIG. 8 is a schematic diagram illustrating the preferred sizing of thefriction-mitigating protuberance(s) of the present invention in arotatable prosthetic heart valve.

FIG. 9 is a cross-sectional diagram of another embodiment where thereare protuberances on the valve body.

FIG. 10 is a cross-sectional diagram of another embodiment where thereare protuberances on the valve body.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The detailed description set forth below in connection with the appendeddrawings is intended as a description of the presently preferredembodiments of the invention, and is not intended to represent the onlyforms in which the present invention may be constructed or utilized. Thedescription sets forth the functions and the sequence of steps forconstructing and operating the invention in connection with theillustrated embodiments. It is to be understood, however, that the sameor equivalent functions may be accomplished by different embodimentsthat are also intended to be encompassed within the spirit and scope ofthe invention.

Suture rings for rotatable prosthetic heart valves of the presentinvention are illustrated in FIGS. 1-8. These figures include showingsof two (2) presently preferred embodiments of the invention--one foraortic valve replacement and the other for mitral valve replacement.However, such figures and the accompanying description is by way ofexample only and not by way of limitation. Those skilled in the art willappreciate that the sewing ring of the present invention may be utilizedin various other applications.

In general, the present invention provides prosthetic heart valves whichcomprise an annular valve body having at least one occluder member(e.g., a pair of pivoting leaflets) positioned therewithin. A rotatablesuture ring 10, 110 is mounted about the outer surface of the annularvalve body 34, 134. Such suture ring 10, 110 comprises a ring member 12,112 having an annular sponge 14, 114 disposed thereabout, and a fabricmaterial 16, 116 covering. The fabric material 16, 116 may comprise aknitted or woven material with or without a velour structure, frompolytetraflouroethylene, polypropylene or polyester. The fabric material16, 116 is preferably formed as a seamless tube. The fabric material 16,116 extends into the region between the ring member 12, 112 and theouter surface of the annular heart valve body 34, 134. At least onefriction-mitigating protuberance, such as an annular rib 36, 136 whichserve to decrease the friction-creating surface area which exertspressure upon the portion of the fabric material 16, 116 which iscaptured between the heart valve body 34, 134 and the ring member 12,112. In this manner, such protuberance, such as an annular rib 36, 136,serves to control and limit the frictional resistance to rotation of thesuture ring 10, 110 despite normal variations in the thickness of thefabric material 16, 116.

It will be appreciated that, as an alternative to forming theprotuberance, such as an annular rib 36, 136 on the ring member 12, 112,such protuberances, such as annular rib(s) may alternatively be formedon the outer surface of the heart valve body 34, 134 to thereby producethe same friction-mitigating effect.

Description of The Suture Ring For a Rotatable Mitral Valve

Referring now to FIGS. 1-3a, the first embodiment of the presentinvention generally comprises a suture ring 10 configured for use withan artificial mitral valve. The suture ring 10 generally comprises aring member 12 to which an annular sponge 14, formed of silicone rubberor other material, is attachable. A fabric material 16 generally coversthe ring member 12 and the annular sponge 14, as discussed in detailbelow.

Accordingly to the first preferred embodiment of the present invention,the ring member 12 comprises an outer surface 18, an inner surface 20, aproximal edge 22, and a distal edge 24. A plurality of apertures 26extend through the ring member 12, (i.e., from the outer surface 18 tothe inner surface 20 thereof), so as to facilitate sewing of the fabricmaterial 16 thereto.

The ring member 12, further comprises an annular tracking rib 28 whichis configured to be received within a generally complimentary annulartracking groove 30 formed in an outer surface 32 of the annular valvebody 34.

The ring member 12, further comprises at least one, preferably twoprotuberances, formed upon the inner surface 20 of the ring member 12 soas to mitigate the frictional resistance to rotation which results fromcompression of the fabric material 16 which is interposed between theinner surface 20 of the ring member 12 and the outer surface 32 of theannular valve body 34, as best shown in FIG. 6 and described in detailbelow. The protuberances preferably define first 36 and second 38annular ribs, preferably formed adjacent the distal 24 and proximal 22edges of the ring member 12, respectively.

As used herein, the term proximal refers to that end or edge of thedevice which is on the upstream blood flow side thereof and the termdistal refers to that end or edge of the device which is on thedownstream blood flow side of the device. The proximal end of the deviceis indicated in the drawings by the letters PE and the distal end of thedevice is indicated in the drawings by the letters DE.

Alternatively, the such protuberances may be formed upon the annularvalve body 34, so as to achieve a like effect, wherein the frictionalresistance to rotation due to compression of the fabric material betweenthe inner surface 20 of the ring member 12 and the outer surface 32 ofthe annular valve body 34 is likewise substantially mitigated.

According to the preferred embodiment of the present invention, the ringmember 12 is comprised of a polyacetal material, one example of which isDELRIN (a registered trademark of E. I. Du Pont De Nemours & Co., Inc.,Wilmington, Del.). As those skilled in the art will appreciate, the ringmember 12 may be comprised of various other polymer materials such aspolyacetals, polyesters, ultra high molecular weight polyethylene,polysulfones, polyimides, polyether keytones (e.g., PEEKs), liquidcrystalline polymers (e.g., LCPs), and/or carbon fiber composites. Thering member may alternatively be formed of a biocompatable metal ormetal alloy, such as titanium, Elgiloy, or zirconium.

If formed of a polymer material, required tolerances for the ring (e.g.,as an ellipse) member are reduced. Indeed, the ring member may formed,in an out-of-round condition, since attachment to a valve body willforce the ring member to assume the desired annular shape.

According to the preferred embodiment of the present invention, the ringmember 12 is generally rigid, such that a tool or fixture (FIG. 8) istypically required to effect installation of the suture ring 10 upon theannular valve body 34. Alternatively, the ring member 12 may besubstantially flexible and use of the installation tool may be optional.

The annular sponge 14 is comprised of a biocompatable resilientmaterial, preferably silicone rubber. Those skilled in the art willappreciate that various other needle penetrable materials, such as feltor a textile or polymer fabric filler, may likewise be suitable for useas the annular sponge 14. The needle-penetrable annular sponge 14preferably comprises a plurality of cells 39 (best shown in FIG. 3a),which enhance the resiliency thereof, so as to facilitate desireddeformation of the flange or outer periphery 11 (FIG. 1) of the suturering 10, thereby allowing it to conform to the natural mitral root, soas to maximize the orifice to annulus ratio. The cells 39 also make thesuture ring 10 more easily penetrable by a needle and mitigate dullingof the needle, as would occur if a solid annular member were utilizedinstead of a sponge.

The needle-penetrable fabric material 16 preferably comprises abiocompatible woven or knitted material, such as polyester or othersuitable material. The fabric may be treated or coated with variouschemical materials/coatings to improve biocompatability (e.g., heparin,chemically-bound heparin, carbon coatings, etc.).

Depending on the manufacturing or weaving methods used, and variationsin the source of supply from which the material is obtained, theneedle-penetrable fabric material may be subject to some variations inthickness. For example, the typical woven polyester material used forthis application varies from approximately 0.008 inch to approximately0.014 inch in thickness. In view of this typical variation in thethickness of the needle-penetrable fabric material 16, the frictionmitigating protuberances of the present invention, such as the first 36and second 38 annular ribs, will be sized relative to the thickness ofthe fabric material interposed therebetween, so as to permit routinerotation of the suture ring 10 relative to the annular valve body 34over the entire range of fabric thicknesses wherein theneedle-penetrable fabric material 16 is expected to vary.

Referring now to FIG. 6, the fabric material 16 is preferably sewed tothe ring member 12 at both the distal and proximal end thereof. Thefabric material 16 is sewn to the ring member 12 at the distal endthereof by repeatedly passing a biocompatable thread through apertures26 so as to sew the fabric material to both the outer surface 18 and theinner surface 20 of the ring member 12.

In a similar fashion, the fabric material 16 is sewed to the proximalend of the ring member 12 by repeatedly passing biocompatible threadthrough apertures 26 at the proximal end of the ring member 16. This ispreferably accomplished by passing the thread through the fabricmaterial 16 on the outer surface 18 of the ring member 12 at the corner19 formed by the annular sponge 14 and the ring member 12. Such sewingof the fabric material 16 to the ring member 12 assures that the fabricmaterial 16 is pulled tightly into the corner 19 and also held tightlyalong the surfaces of the annular sponge 14 and the ring member 12.

Operation of the Rotatable suture Ring Mounted on a Prosthetic MitralValve

Referring now to FIG. 6, operation of the suture ring for a rotatableartificial mitral valve is illustrated. According to the preferredembodiment of the present invention, a torque control gap 40, having awidth of dimension A, is defined by the first annular rib 36 at theproximal or inflow end PE of the valve. In a similar fashion, a secondgap 42, dimension C, is formed at the distal or outflow end DE of thevalve.

The torque control gap 40 is configured to have a gap width, dimensionA, which compresses the fabric material 16 captured between the firstannular rib 36 and the annular valve body 34 sufficiently to provide adesired degree of frictional resistance to rotation. Thus, the ease withwhich the annular valve body 34 is rotatable within the suture ring 10is substantially determined by the width, dimension A, of the torquecontrol gap 40.

As those skilled in the art will appreciate, frictional resistance torotation of the annular valve body 34 within the suture ring 10 must besufficient to prevent undesirable or inadvertent rotation thereof afterthe annular valve body 34 has been rotated to a desired orientation bythe physician. Thus, once the annular valve body 34 has been oriented asdesired, the frictional resistance to rotation must be sufficient tomaintain the annular valve body 34 at the desired rotational orientationthereof. As such, a minimum frictional resistance to rotation isdefined.

As discussed in detail above, the frictional resistance to rotation mustbe less than that amount which would require excessive force by thesurgeon and/or which could result in damage to the annular valve body34, suture ring 10, and/or the patient. Thus, a maximum frictionalresistance to rotation is definable for each particular design and typeof valve.

By sizing the torque control gap 40 such that its width corresponds to agiven thickness of fabric material 11, a desired compression of thefabric material 11 is provided and the frictional resistance to rotationis maintained within the desired range. In this manner, the width,dimension A, which corresponds to the normal range of thickness andcoefficient of friction of the fabric material 16, such that sufficientfrictional drag will be produced to prevent inadvertent rotation of thesuture ring 10 on the valve body 34.

The second gap 42 defined by the annular rib 38 on the proximal end ofthe suture ring 10 is sized so as to provide minimal frictionalresistance to rotation for a given thickness of fabric material 16. Thegap 42, defined by dimension C, is however sufficiently small tosubstantially prevent leakage of blood into the second void 37 formedintermediate the ring member 12 and the annular valve body 34. In asimilar fashion, substantial blood leakage into the first void 39 formedintermediate the ring member 12 and the annular valve body 34 isprevented by the compression of the fabric material 16 within thenarrower torque control gap 40.

Thus, the first or torque control gap 40 is preferably smaller than thesecond gap 42, such that the contribution to the frictional resistanceto rotation from the second gap 42 is substantially less than that fromthe first gap 40.

Thus, according to the present invention, compression of the fabricmaterial 16 between the ring member 12 of the suture ring 10 and theannular valve 34 is both substantially minimized and controlled.Compression of the fabric material 16 is substantially minimized sinceonly a portion of the fabric material 16 interposed between the ringmember 12 and the annular valve 34 is compressed. Most of the fabricmaterial 16 interposed between the ring member 12 and the annular valvebody 34 is disposed within the first 39 and second 37 voids, both havinga width, dimension B, which is substantially greater than dimensions Aand C, such that the fabric material within the voids 37, 39 is notsubstantially compressed. As discussed in detail above, compression of aportion of the fabric material 16 is controlled by matching the torquecontrol gap 40, dimension A, to the thickness of the fabric material 16.

Thus, according to the present invention, after the suture ring 10 hasbeen sewn in place upon the endogenous valve annulus of thepatient-host, then the valve is rotated, preferably using a tool, so asto prevent damage to the occluder leaflets thereof, to a desiredposition. By controlling the resistance of the rotation of the valvebody 34 within the suture ring 10, it is assured that the valve can beso rotated without the application of excessive torque thereto. Thus,the potential for damage to the suture ring, valve, and/or endogenoustissue is mitigated.

After the valve has been rotated to the desired orientation thereof, thefrictional resistance to rotation is sufficient to maintain the valve inthe desired position.

Description of the Suture Ring For a Rotatable Aortic Valve

Referring now to FIGS. 4 and 5, the second embodiment of the presentinvention generally comprises a suture ring 110 configured for use withan artificial aortic valve. As in the mitral valve discussed above, thesuture ring 110 generally comprises a ring member 112 to which anannular sponge 114 is attached. A fabric material 116 generally coversthe ring member 112 and the annular sponge 114.

As in the first embodiment of the present invention, the ring member 112comprises an outer surface 118, an inner surface 120, a proximal edge122, and a distal edge 124. A plurality of apertures 126 extendthroughout the ring member 112.

The ring member 112 of the second embodiment thereof further comprisesan annular tracking rib 128 which is configured to be received within agenerally complimentary annular tracking groove 130 formed in the outersurface of the annular valve body 134 of the aortic valve. The ringmember 112 further comprises first 136 and second 138 annular ribs,preferably formed adjacent the distal 124 and proximal 122 edges of thering member 112, respectively.

Thus, the suture ring 110 of the second embodiment of the presentinvention is generally similar to that of the first embodiment thereof.One important exception is that the configuration of the sponge member114 is generally conical in shape, thus defining a substantiallyconstant taper from the proximal end to the distal end thereof, suchthat the distal end has a substantially greater diameter than theproximal end of the sponge member 114. Additionally, the valve body 134of the aortic valve, as well as the sewing ring 110 therefor, are ofslightly less diameter than in the mitral valve.

The sponge member 114 preferably comprises open cells 115, whichcontribute to the resiliency thereof, and also facilitate sewingtherethrough, as discussed regarding the first embodiment of the presentinvention.

The fabric material 116 is preferably sewed to the ring member 112 arerepeatedly passing biocompatible thread through the apertures 126 on thedistal end of the ring member 112 and then repeating the process for theproximal end thereof. During such sewing, the thread passes through theannular sponge 114 on both the distal and proximal ends of the ringmember 112.

The ring member 112 preferably comprises an annular tracking rib 128which was received within a generally complimentary annular trackinggroove 130 formed upon the annular body 134 of the aortic valve.

Operation of the Rotatable Suture Ring Mounted on a Prosthetic AorticValve

Referring now to FIG. 7, operation of the suture it ring 110 for arotatable artificial aortic valve is illustrated. According to thepreferred embodiment of the present invention, the torque control gap140, having a width of dimension A, is defined by the first annular rib136 at the proximal end of the suture ring 110. In a similar fashion, asecond gap 142, dimension C, is formed at the proximal end of the suturering 110.

The relative sizing (width) and functions of the torque control gap 140and the second gap 142 are the same as described hereabove with respectto the first embodiment of the present invention.

Assembly of the Rotatable Heart Valves of the Present Invention

The suture ring 10, 110 may be mounted upon the heart valve body 34, 134by any suitable means. Preferably, the rigid ring member 12, 112 isformed of material which may be elastically expanded to a sufficientdegree to permit the suture ring 10, 110 to be snap-fit onto the valvebody 34, 134 such that the tracking rib 28, 128 of the suture ring 10,110 becomes positioned within the tracking groove 30, 130 of the heartvalve body 34, 134.

Such expansion of the rigid ring member 12, 112 may be accomplished byinserting outwardly moveable projections or "fingers" within theassembled sutured ring 10, 110 as it is being snap-fit onto the heartvalve body 34, 134. Alternatively, a tapered, frusto conical dilator maybe utilized to dilate the rigid ring member 12, 120 of the suture ring10, 100 as the suture ring 10, 100 as the suture ring 10, 100 is beingsnap fit onto the heart valve body 34, 134.

Preferred sizing of the Suture Ring For Minimally Invasive SurgicalImplantation

Various minimally invasive surgical procedures are presently beingdeveloped to permit surgical valve replacement in a human heart throughminimal access incisions, typically no more than 0.5-1 inch in length.Typically, these minimally invasive surgical techniques employ the useof one or more thorascopes to permit the surgeon to visualize theinterior of the thoracic cavity, and the concomitant deployment of oneor more endoscopic surgical instruments (e.g., thoracoscopes) into thethoracic cavity through minimal access incisions formed at desiredlocations about the thorax of the patient.

In light of these recently-developed minimally invasive surgicaltechniques, it is desirable that at least some of the embodiments of thepresent invention be constructed in a manner which minimizes the size ofthe prosthetic valve in at least one dimension, thereby facilitatingpassage of the valve into the thoracic cavity and into its intendedintracardiac implantation site, through relatively small minimal accessincisions or openings.

In this regard, it is desirable that the longitudinal length L of theaortic or mitral sewing ring 10, 110 be no greater than the longitudinallength L₂ of the valve body.

By minimizing the length of the suture ring 10, 110 such that it doesnot protrude beyond the longitudinal ends of the valve body 34, 134, thelongitudinal length of the prosthetic valve/suture ring assembly isminimized.

It is understood that the examples and embodiments described herein andshown in the drawings represent only the presently preferred embodimentsof the invention, and are not intended to exhaustively describe indetail all possible embodiments in which the invention may take physicalform. Indeed, various modifications and additions may be made to suchembodiments without departing from the spirit and scope of theinvention. For example, various different cross sectional configurationsof the sewing ring are contemplated. As those skilled in the art willappreciate, the annular sponge thereof may be configured so as tofacilitate attachment to various modified configurations of theendogenous valve annulus. Further, various different configurations ofthe annular tracking rib of the sewing ring member and/or the annulartracking groove of the valve body may likewise be suitable.

What is claimed is:
 1. An artificial heart valve having a controlledresistance to torque, comprising:an annular valve body having oppositelongitudinal ends, a blood flow passageway therethrough, and an outersurface; a suture ring mounted on the outer surface of the valve body tobe relatively rotatable therewith, the suture ring including an innersurface, an outer surface, a proximal edge, and a distal edge; aneedle-penetrable sheet being interposed between the inner surface ofthe suture ring and the outer surface of the valve, the sheet having athickness; and at least one protuberance formed on either the outersurface of the valve body or the inner surface of the suture ring forcompressing the sheet therebetween, a majority of the sheet interposedbetween the inner surface of the suture ring and the outer surface ofthe valve otherwise being uncompressed, the protuberance having a heightforming a gap between the inner surface of the suture ring and the outersurface of the valve body, the height of the protuberance and thus thesize of the gap being dependent on the thickness of the sheet so thatthe torque required to rotate the valve body with respect to the suturering is maintained within a range having a minimum above that at whichthe valve body would freely rotate within the suture ring and a maximumbelow that which would require excessive force to turn the valve bodywithin the suture ring.
 2. The valve of claim 1, wherein theprotruberance is formed circumferentially around the outer surface ofthe valve body or the inner surface of the suture ring.
 3. The valve ofclaim 2, wherein the protruberance is an annular rib.
 4. The valve ofclaim 3, wherein there are two annular ribs of equal height.
 5. Thevalve of claim 1, wherein the sheet is a fabric having a thickness ofbetween 0.008 inch and 0.014 inch.
 6. The valve of claim 1, wherein thesheet is a fabric and the suture ring comprises a ring member and asurrounding sponge member, the fabric sheet extending around the suturering and around the proximal and distal edges thereof to pass inbetweenthe suture ring and valve body at both longitudinal ends.
 7. The valveof claim 6, wherein the fabric sheet is a single piece.
 8. The valve ofclaim 6, wherein the ring member is a polyacetal and the protruberancecomprises a pair of annular ribs projecting inwardly therefrom.
 9. Anartificial heart valve having a controlled resistance to torque,comprising:an annular valve body having opposite longitudinal ends, ablood flow passageway therethrough, and a rigid outer surface; a suturering mounted on the outer surface of the valve body to be relativelyrotatable therewith, the suture ring including a generally rigid innersurface, an outer surface, a proximal edge, and a distal edge; aneedle-penetrable sheet being interposed between the inner surface ofthe suture ring and the outer surface of the valve body, the sheethaving a longitudinal dimension extending between the inner surface ofthe suture ring and the outer surface of the valve body, the sheet beingcompressed within a gap formed between the generally rigid inner surfaceof the suture ring and the rigid outer surface of the valve body tosubstantially determine the torque required to rotate the valve bodywith respect to the suture ring, the sheet extending into voids alongmost of its longitudinal dimension, the voids defined intermediate theinner surface of the suture ring and the outer surface of the valvebody, and the sheet not being compressed in the voids so that the torquerequired to rotate the valve body with respect to the suture ring ismaintained within a range having a minimum above that at which the valvebody would freely rotate within the suture ring and a maximum below thatwhich would require excessive force to turn the valve body within thesuture ring.
 10. The valve of claim 9, wherein the sheet is a fabric andthe suture ring comprises a ring member and a surrounding sponge member,the fabric sheet extending around the suture ring and around theproximal and distal edges thereof to pass inbetween the suture ring andvalve body at both longitudinal ends.
 11. The valve of claim 10, whereinthe fabric sheet is a single piece.
 12. The valve of claim 9, whereinthe suture ring includes a pair of annular ribs projecting inwardlytherefrom which contact and compress the fabric sheet against the valvebody.
 13. The valve of claim 12, wherein the two annular ribs are ofequal height.
 14. The valve of claim 12, wherein the sheet is a fabricand has a thickness of between 0.008 inch and 0.014 inch and the heightof the annular ribs is dependent on the thickness of the sheet.